An initial clean up of the Digest mechanism following the move away from dispatching within the mechanism.
[UNDERTOW-34] Update Digest credential handling to allow for the prepared ha1 to be intercepted and to remove all use of the plain text password within the Undertow side of digest handling.
Clean up the embedded builder API, and add static utility methods for creating handlers
Move cookies directly onto the exchange, which makes the API a lot cleaner and removes the need for the CookieHandler